Biological Effects of Light-Emitting Diode (LED)- Based Low-Level Light on Natural Killer Cells

Natural killer (NK) cells have attracted considerable attention as a promising strategy for cancer immunotherapy, leading to research efforts aimed at enhancing their efficacy. However, despite the availability of various approaches to enhance NK cell function, there remains an urgent need for more efficient, cost-effective, and safe methods. Energy metabolism plays a critical role in the activation of NK cells. Low levels of light can influence cellular energy metabolism, thereby affecting cellular activity. In this study, we applied low-level light to human-derived NK-92 cells to investigate the changes in cellular activity induced by alterations in energy metabolism. Exposure to a 740 nm lightemitting diode (LED) at an energy density of 3 J/cm² once daily for 3 consecutive days resulted in the most significant changes in adenosine triphosphate (ATP) levels. Furthermore, NK-92 cells produced ATP in a glycolysis-dependent manner, and exposure to 740 nm light further promoted the glycolytic process. Additionally, 740 nm light stimulation prevented apoptosis in cells and enhanced the cytotoxicity of NK-92 cells. In conclusion, these findings suggest that LED-based low level light therapy is a viable approach for enhancing the efficacy of NK cells.